1. Field of the Invention
The invention is directed to a self-pumping hydropneumatic suspension strut with internal height control, in particular for motor vehicles with a work cylinder which is filled with oil and is under pressure by at least one gas cushion which is arranged in a high-pressure chamber and which acts as a spring, the work cylinder being divided into two work spaces by a work piston supported by a hollow piston rod, with a piston pump which is driven by the spring movements and conveys oil out of a low-pressure chamber into the work space connected to the high-pressure chamber and connects the work space connected to the high-pressure chamber to the low-pressure chamber by a regulating opening which is closable depending on the position of the work piston in the work cylinder, wherein a flow connection running through an intermediate wall and opening out below the surface of the oil is provided between the pump space and the low-pressure chamber.
2. Description of the Related Art
Self-pumping hydropneumatic suspension struts with internal height control in which the work cylinder is under the pressure of at least one gas cushion arranged in a high-pressure chamber and acting as a spring are already known (EP 0.033.839 A2). Together with a pump rod, the hollow piston rod forms a piston pump so that a damping medium is conveyed out of a low-pressure chamber into the work space connected to the high-pressure chamber by means of the spring movements of the vehicle body relative to the vehicle chassis. This suspension strut is a mono-tube construction in which the high-pressure chamber is arranged axially behind the work spaces in the outer tube and wherein this high-pressure chamber separates the damping medium from the gas under pressure by a dividing piston. The high-pressure chamber and the low-pressure chamber are separated from one another by an intermediate wall which has the additional object of holding the pump rod in a springing manner. The springing retention of the pump rod serves to reduce the susceptibility of the pump to shocks. This embodiment form is disadvantageous in that the suction tube exiting from the low-pressure chamber penetrates the intermediate wall and subsequently opens out into the pump chamber again through the intermediate wall. This design requires a relatively large outer diameter and, so as not to further enlarge the outer diameter, the suction tube is tightly glued into the intermediate wall. Great stress is placed upon this glue connection due to the high pressure in the high-pressure chamber and the springing pump rod movement. The helical construction of the suction tube has a high suction resistance with respect to the total length, particularly in cold temperatures, and consequently would have to have a correspondingly large clear inner diameter so that an increased outer diameter of the overall suspension strut would have to be taken into account again.